The Webasto Thermo Top Z heater kit is a variant of the popular Thermo Top range that has been designed by Webasto to supplement a vehicles heating system and works in conjunction with the vehicles cooling system.
As modern diesel engines are highly efficient there is too little usable waste heat from the engine available to heat the vehicle on cold days.
Technically, the Thermo Top Z heater works just like a parking heater - although it only functions while the engine is running, and does not have its own circulation pump fitted, as the water is circulated by the water pump on the vehicle's engine.
When the ambient temperature is below 5°C, the Webasto heater cuts in to provide extra heat for the cooling circuit, enabling the cabin and engine to get up to optimum operating temperature.
This heater can be upgraded to operate as a full parking heater, if required, although this is only a viable option if the heater is already fitted to the vehicle, as many are original equipment items, fitted by the manufacturers from new. Upgrade kit 89247D required.